provenance

Where state was read: at the caller's call site, or in the element's own deferred event.

Recorded rather than left to be inferred. Under caller-owned timing the interval length is very nearly a giveaway for which entry point was used, and inference from a near-giveaway is how a subtle bias enters a learner. A consumer that wants only states the library guaranteed consistent filters on DEFERRED; one that does not, at least knows its dataset is mixed.